YAO Yunhui, MA Wei, CUI Songyun, QI Dexuan and GAN Jiawei

Abstract: Under the joint action of six-key-project management system in Dianchi Lake basin, the water quality of the Waihai and Caohai in Dianchi Lake has been improved significantly in recent years. Caohai, the carrier for pollutant discharge in Dianchi Lake, has been gradually transformed into a place of leisure and entertainment for residents and name card for the city. In order to adapt to the orientation of the func-tional change of Caohai and accelerate the water quality improvement in the sensitive Lake areas, new eco-project was implemented, such as emergency water supply project of Niulan River-Caohai, new eco-puri-fication project of Laoyunliang River and water replacement channel project of Haigeng levee. The clean and sewage water was physically isolated and separated through new eco-purification project of Laoyunliang River. The emergency water supply project of Niulan River-Caohai provided the necessary water resources conditions for intercepting pollution around the lake and separating clean and sewage water. Water replacement channel project of Haigeng levee shortened the water replacement period in the clean water area and provided hydrodynamic guarantee for water landscape in environmental sensitive areas. As the result, the TN and TP were reduced by 15%~28%. Water replacement channel project will improve the internal accumulation condition and be conductive to the continuous improvement of water quality in Caohai. These combined project managements can improve water quality of Caohai.

Keywords: water pollution control; engineering measure; sewage diversion; Caohai Lake; Dianchi Lake